RADIOLARIANS AND CONODONTS FROM CALCAREOUS CONCRETIONS IN THE MIDDLE PENNSYLVANIAN EXCELLO AND LITTLE OSAGE SHALES IN MISSOURI AND ILLINOIS

Early diagenetic calcareous concretions in the black phosphatic shale facies of the Middle Pennsylvanian Excello Shale (Mouse Creek Formation of the Midcontinent Basin and Carbondale Formation of the Illinois Basin) often contain an abundant and diverse radiolarian and conodont fauna. Siliceous sponge spicules, fecal pellets, foraminifers and fish material also occurs. At the neostratotype of the Excello Shale (Henry Co., MO) moderately abundant radiolarians, Pseudoalbaillella spp. and Entactinia spp., occur as relatively poorly preserved casts and internal molds of silica, calcite, and pyrite. Conodonts species including Gondolella wardlawi, Idiognathodus acutus, Neognathodus roundyi, are moderately abundant. At Jubilee College State Park (Peoria Co., Illinois), the Excello Shale, below the Covel Conglomerate, is dark gray and much thinner than at the neostratotype section. It contains a very abundant radiolarian (estimated and extrapolated millions per kilogram) and conodont fauna (over 1500 P1 elements per kilogram). Thin sections show many concretions are radiolarian packstones, with most preserved as calcite replacements of original opal-A. Species include Pseudoalbaillella annulata, Albaillella sp., Entactinia sp., and an unnamed Pseudoalbaillella species also seen in the Excello of southeast Kansas. Conodonts include Gondolella wardlawi, Neognathodus roundyi, Neognathodus dilatus, Idiognathodus acutus, and Adetognathus sp. The Midcontinent Little Osage shale equivalent, above the Covel Conglomerate, at Fargo Run 1.5 miles southeast of Jubilee College Park contains a poorly preserved radiolarian fauna of pseudoalbaillellids and entactinids along with sparse conodonts. Triangular radiolarian forms (e.g., Latentifistula spp., Latentidiota spp., and Quadriremis spp.) reported by Nestell, Pope, and Nestell in Iowa, have not been found at the Missouri and Illinois locations.